Sueppong GowachirapantAlida Melse-BoonstraPattanee WinichagoonMichael B. ZimmermannWageningen University and Research CentreMahidol UniversityInternational Council for the Control of Iodine Deficiency Disorders (ICCIDD) Global NetworkEcoles polytechniques federales2018-11-092018-11-092014-01-01Maternal and Child Nutrition. Vol.10, No.1 (2014), 61-7117408709174086952-s2.0-84890559950https://repository.li.mahidol.ac.th/handle/20.500.14594/34710Hypothyroxinaemia early in pregnancy may impair fetal brain development. Increased body weight has been associated with low thyroxine concentrations in non-pregnant women. In pregnant women, morbid maternal obesity is a risk factor for thyroid dysfunction. But whether lesser degrees of overweight that are much more common could be a risk factor for hypothyroxinaemia in pregnancy is unclear. The objective of this study was to investigate if overweight increases risk for thyroid dysfunction, and specifically hypothyroxinaemia, in iodine-deficient pregnant women. We performed a cross-sectional study at first hospital visit among healthy Thai pregnant women. We measured weight and height, urinary iodine concentration (UIC), serum thyroid hormones and thyroglobulin. Pre-pregnancy weight and relevant dietary factors were determined by questionnaire, and body mass index (BMI) was used to classify weight status. Among 514 women (mean gestational age, 11 weeks) with a median UIC of 111μgdL-1, indicating mild iodine deficiency, 12% had low free thyroxine (fT4) concentrations: 3% had overt hypothyroidism; 7% had subclinical hypothyroidism; and 8% had isolated hypothyroxinaemia. Based on pre-pregnancy BMI, 26% of women were overweight or obese. In a multiple regression model, BMI was a negative predictor of fT4 (β=-0.20, P<0.001). Compared to normal weight women, the prevalence ratio (95% CI) of a low fT4 in overweight women was 3.64 (2.08-6.37) (P<0.01). Iodine-deficient pregnant Thai women who are overweight have a 3.6-fold higher risk of hypothyroxinaemia in the first trimester compared to normal weight women. Targeted screening should consider overweight a potential risk factor for thyroid dysfunction in pregnant women in iodine-deficient areas. © 2013 John Wiley & Sons Ltd.Mahidol UniversityMedicineNursingArticleSCOPUS10.1111/mcn.12040